In the formation of color paper it is known that the base paper has applied thereto a layer of polymer, typically polyethylene. This layer serves to provide waterproofing to the paper, as well as providing a smooth surface on which the photosensitive layers are formed. The formation of a suitably smooth surface is difficult requiring great care and expense to ensure proper laydown and cooling of the polyethylene layers. One defect in prior formation techniques is caused when an air bubble is trapped between the forming roller and the polyethylene which will form the surface for casting of photosensitive materials. This air bubble will form a pit that will cause a defect in the photographic performance of photographic materials formed on the polyethylene. It would be desirable if a more reliable and improved surface could be formed at less expense.
In color papers there is a need for providing color papers with improved resistance to curl as proposed in U.S. patent application Ser. No. 08/864,228 filed May 23, 1997. Present color papers will curl during development and storage. Such curl is thought to be caused by the different properties of the layers of the color paper as it is subjected to the developing and drying processes. Humidity changes during storage of color photographs lead to curling. There are particular problems with color papers when they are subjected to extended high humidity storage such as at greater than 50% relative humidity. Extremely low humidity of less than 20% relative humidity also will cause photographic papers to curl.
In photographic papers the polyethylene layer also serves as a carrier layer for titanium dioxide and other whitener materials as well as tint materials. It would be desirable if the colorant materials rather than being dispersed throughout the polyethylene layer could be concentrated nearer the surface of the layer where they would be more effective photographically.
The utilization of currently available photographic papers includes treatment that extends beyond the photoprocessing and typical trimming operations. In many cases the additional treatments are performed on portraits or large format commercial images to enhance and provide a distinctive visual appearance to the image. Examples of such treatments include liquid sprays, protective laminations, surface embossing, and lamination to materials of highly textured surfaces. In the lamination of an image to a highly textured surface the thickness of the substrate supporting said photographic image will directly influence the extent of the transfer of the texture to the viewer. Reducing the thickness of the image layer is necessary to provide the desired visual effect. Current practice to reduce the thickness of the image layer involves the stripping of the photographic image layer and the adjacent polyethylene layer from the paper core of current photographic papers. The stripping of the image layer and adjacent polyethylene layer from the paper substrate found in current papers is difficult and time consuming due to variability in the cohesion and adhesion properties found in the layers comprising the photographic materials. During the stripping process, an operator will provide uniform pull force to separate the image layers from the substrate. Non-uniform force can cause fracture of the photographic material at an interface other than that between the polyethylene layer and the paper substrate or in the most severe case, damage to the image.
It has been proposed in U.S. Pat. No. 5,244,861 to utilize biaxially oriented polypropylene in receiver sheets for thermal dye transfer.